The invention relates to an engine hood for a motor vehicle having an outer planking and an inner part. Between the outer planking and the inner part, a supporting part is arranged which reinforces the outer planking.
In order for an engine hood to absorb sufficient energy in case of an impact with a pedestrian, it is known from production vehicle construction to arrange the engine hood at a sufficient distance above the assemblies arranged below the engine hood. The determination of the so-called HIC (head injury criterion) indicates whether an engine hood meets the legal requirements.
From International patent document WO 03/011660 A1, it is known to equip an outer planking or cover with a reinforcing layer. The reinforcing layer is arranged above the outer planking and is connected with the outer planking. The reinforcing layer consists of a brittle material, so that the hood has a buckling strength required for normal operation. In the case of a dynamic loading, for example, in the event of a head impact, the supporting layer will break while absorbing energy, so that a deceleration pattern occurs that is favorable for a head impact.
However, as a result of the different materials, the manufacturing expenditures are increased.
It is an object of the invention to reduce the manufacturing costs for an engine hood of a motor vehicle while maintaining a favorable deceleration pattern in the event of a head impact.
According to the invention, an engine hood for a motor vehicle has an outer planking and an inner part, between the outer planking and the inner part a supporting part being arranged which reinforces the outer planking. The supporting part has supporting elements which, in the event of an essentially vertical admission of force, permit a displacement of the outer planking relative to the inner part until the supporting part rests with its predominant surface against the inner part.
Advantageous further developments of the invention are described and claimed herein.
According to the invention, a supporting part reinforcing the outer planking is to be provided between the outer planking and an inner part, particularly in the forward region of the engine hood, which supporting part has supporting elements that, in the event of a vertical admission of force, permit a displacement of the outer planking relative to the inner part until the supporting part rests with its predominant surface against the inner part.
Within the context of the invention, supporting elements are such that, up to a certain degree, they are held in a flexible or elastic manner; that is, when the force effect is low (for example, during a normal driving operation or when opening or closing the engine hood), the supporting elements move back into their initial position; when the force exceeds a previously defined value, the supporting elements deform plastically while absorbing energy. In this case, the supporting elements can either support themselves at the inner part or the outer planking supports itself on the supporting elements. The supporting part itself together with its supporting elements can be constructed as a sheet metal part, particularly as a deep-drawn part, so that the same materials are processed together.
A reinforcement of the engine hood in the forward region can be achieved when the inner part and the outer planking at least partially form a closed hollow profile.
In order to obtain a favorable delay pattern also in the event of a pedestrian impact in the edge regions of the engine hood, the supporting part can extend essentially over almost the entire engine hood width.
The supporting part, preferably, is a flat component whose essential dimensional surface may be constructed to be planar but may also be physically curved. It is recommended that the dimensional surface of the supporting part at least partially follow the course of the outer planking. In order to implement the desired relative movement of the supporting part with the outer planking with respect to the inner part, supporting elements may project at an angle from the dimensional surface of the supporting part.
Optionally, the supporting elements may project from the supporting part in a step-shaped manner in the direction of the inner part, in which case the supporting elements may project from the longitudinal sides of the supporting part in the direction of the inner part.
In an alternative embodiment, the supporting elements may project in the direction of the outer planking, in which case several supporting elements are arranged side-by-side in the transverse direction of the vehicle distributed over the width of the engine hood.
In a longitudinal sectional view, in an alternative embodiment, the supporting part may extend in a step shape within the hollow profile. This has the advantage that, in the event of a vertical force, this step bends open while additionally absorbing energy.
This step may be defined in that the supporting part extends from an approximately horizontally extending floor wall to an approximately vertically extending rearward face wall of the inner part. Under the effect of a force, a forced movement of the supporting part is therefore made possible.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.